McConnell Dowell has won a contract for submarine and land-based pipelines to improve and futureproof the treatment of wastewater for three communities in Christchurch, New Zealand.

The package of work for the Governor's Bay, Diamond Harbour and Lyttelton wastewater project is for pipelines to convey untreated wastewater to the Christchurch Treatment Plant in Bromley. After treatment, wastewater will be discharged out to sea through the Christchurch Ocean Outfall, which was constructed by McConnell Dowell eight years ago.

Installation of the two (5km and 1.8km) weighted HDPE marine pipelines will involve prefabrication of pipe strings onshore before joining and bottom-pulling the pipelines out to the required location. A backhoe dredger and divers will then be employed to excavate the trench, lower the pipeline and backfill.

Work on site will begin in February 2018 and the project is scheduled for completion by Christmas 2018.